Telephone system



May 12, 1925. 1,537,109

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 1o, 1920 9 sheets-sheet 1 May l2, 1925.

J. DAVIDSON, JR

TELEPHONE SYSTEM 9 Sheets-Sheet 2 Filed Aug. 10. 1920 1,537,109 J.DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 1o. 1920 9 sheets-sheet /wen for Jah?al//dsa/l Jr.

May '12, 1925.

` May 12, 1925.

' J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10. 1920 i May l2, 1925.

J. DAVIDSON,y JR TELEPHONE SYSTEM Filed Aug. 10, 1920 May 12, 192s.1,537,109y

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10, 1920 9 Sheets-Sheet 6 I s AL; L+ IH May12, 1925.-

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10. 1920 9 Sheets-Sheet 7 May 12, 1925.1,537,109

J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10,y 1920 9 Sheets-Sheet s lvwwww. W u wl Huw T@ w w du i QNFWI. .JMW i f%\% May 12, 1925.

1,537,109 t J. DAVIDSON, JR

TELEPHONE SYSTEM Filed Aug. 10, 1920 9 Sheets-Sheet 9 y fw Af;

Patented Maly 12, 1925..

PATENT7-0FFficE. n

JOHN DAVIDSON, JR., or TRENTON, NEW JERSEY, nssieNon 'ro AME'RicAN`TELE- PHONE AND TELEGRAPH COMPANY, A conroianrioN or NEW YORK.

TELEPHONE SYSTEM.

Application `filed August 10,v 192,0. VSerial No. 402,632.

To all w/iom t may concern;

Be it known that l, JOHN DAVIDSON, Jr., residing at Trenton, in thecounty of Mercer and'State of New Jersey, haveinvented certainImprovements in Telephone Systems, of which the following is aspeciiication.

This invention relates to methods and means for controlling a switchingIdevice by a plurality of sets of impulses in particular as applied totelephone systems in which the signals for a plurality oi'l trunk linesextending between widely separated oilices are controlled over a singlesignaling` path common to such trunk lines.

In systems of this character it has been proposed to employ, at oppositeends ot the signaling path, switching means for temporarily renderingthe common signaling path individual te the various trunk lines servedthereby, this individualizing apparatus coinprising means fortranslating into code signals the signals initiated by the diii'ereiittrunk lines, means for transmitting over the signaling path the codesignals which are individual to the trunk lines, and means tor receivingand translating code signals into signals individual tothe respectivetrunks.`

Heretotore some systems of this character have been arrangedy for manualtrunling only. It fi's desirable to arrange Vthe trunk circuits sothatthe incoming trunk terminals th'ereo'f may be `extended by automaticswitching Kmeans to mechanical oiiices, to

`manual offices or to man-ual oliic'es yprovided In thisrei with callindicator mechanisms. spect the invention is in the nature of animprovement over the arrangement shown in applicants Patent No.1,493,109, issued May 6, 1924. In order to accomplish thiswithoutsacrificing the efficiency of the trunk circuits for speechtransmission, yit is desirable to transmit all supervisory signals overa common signaling path, thereby tree-ing the tru-nk circuits for thetransmission of high :frequency switch controlling impulses and for thetransmission of speech.

Anobject of the invention is to control a switching device by a code ofimpulses and `by other impulses. This is done by transmitting a code ofimpulses over a circuit to associate a switching device with anothercircuit and transmitting impulses over the latter mentioned circuit tocontrol the switching device.

It is another object `ot the present invention. to provide improvedsignalingk means for systems ot this vcharacter by means ot which codeimpulses 'are transmitted over a common signaling path Jtor controllingthe association of impulse receiving mechanisms with the incoming endsof a plurality of trunk circuits and tor controlling the'transmission otall signals required for superrling automatic mechanism associated withthe distant or incoming end of kthe trunk.

For ythe attainment oi" these objectsof the invention `there is providedat the originating. end ot ,the trunk lines and 'associated signalingpath, apparatus individual to each trunk line responsive to the `seizureothe trunk, for setting up and transmitting a code of impulsesover `thecommon signaling path. These impulses are received at the terminatingend of the signaling path and translated into a switching in'ipulse iiorstarting up a finder switchy for associating impulse receiving mechanismwith vthe trunk takenfor use by the originating operator. The apparatuslat the originating end ot' the trunk lines is also arranged to.transmit further .code impulses over the signaling path for controllingthe application oi ringing current and for controlling the release ofthe connection upon disconnection of the voriginating toll operatorscord circuit trom Ithe employed trunk.

Apparatus individual t0 eachtrunk line is also provided at theterminating end ot' the trunk lines and associated signaling path forsetting up and transmitting over the common signaling path, codes oliimpulses which are received at the originatiiigend ot the signaling pathand translated into signaling impulses for controlling the operation of`a supervisory signal associated with ithe toll `operators cord circuit,which is at `that time connected with a particular trunk circuit. Thissupervisory signal is arranged to give'l theopeiator la dialing signalto apvprise her that dialing impulses may be transmitted, as soon as thekimpulse receiving mechanism has been associated with the terminatingend of they truuk vcircuit with which she has established connection, togive the operator the. usual supervisory signals when the connection hasbeen extended to the distant called line, when the called subscriberresponds, and when the called subscriber restores his receiver to theswitchhook; and to give the operator a flashing signal to indicate thatthe called partly is busy if connection has been established to asubscriber in a distant mechanical otice or that the called subscriberis operating his switehhook for a recall.

For further attaining the objects ot the invention `there are providedmeans for transmitting dialing impulses of relatively high frequency torexample, 800 cycles, which, because oi their relatively high trequencyare readily transmitted over the toll trunk i talking path withoutinterference with the telegraph facilities oi? the trunk, and means fortranslating these impulses at the incoming end of the trunk circuit intodirect current switch controlling impulses.

By the employment of the common signaling path for transmitting allsupervisory signals in conjunction with means for employing highfrequency transmitting and receiving mechanism for transmitting switchcontrolling impulses over t-he trunk circuit, it is possible to utilizethe talking conductors of the trunk for the connection of telegraphapparatus thereto, to prevent tying up expensive signaling apparatuspermanently with a particular toll trunk and thereby obtain a moreetlicient use of the signaling apparatus, and to permit the use of asmany telephone repeaters in the toll trunk as are found necessary forefficient transmission.

The invention may be more readily understood by reference to thefollowing description considered in connection with the accompanyingdrawings, in which Fig. l shows a cord circuit at an originating tolloperators position, a calling subscribers line which may be associatedwith the toll operators position .in any well-known manner, and thecalling jack ot one of the toll trunks appearing before the tolloperators position; Fig. 2 shows relay mechanism individual to theoutgoing end of a toll trunk and code impulse sending mechanismassociated with the outgoing end of' a signaling path common to aplurality ot toll trunks; Fig. 3 shows a receiving and translatingmechanism for receiving code impulses incoming over the signaling path;Fig. i shows a sending mechanism associated with the distant terminatingend of the signaling path and common to a plurality of toll trunks,together with relays individual to the incoming end of one of said tolltrunks for controlling said sending mechanism; Fig. 5 shows a receivingand translating mechanism associated with the distant terminating end ofthe signaling path for receiving code impulses incoming over thesignaling path from the originating toll operators position and forcontrolling the individual relays of the associated group ot trunks;Fig. 6 shows one of a plurality ot iinder switches for associating ahigh frequency impulse repeating mechanism with a toll trunk which hasbeen taken for use, and a selector switch in which the incoming end ofthe toll trunk terminates; Fig. 7 shows a terminating operators cordcircuit and the line oi a subscriber to which the toll connection may beextended; Fig. 8 shows a lamp indicator for association with theoperators cord circuit shown in Fig. 7, on which indicator aregistration oi the number of the line desired may be set up by impulsestransmittedthereto by the toll operator; and Fig. 9 shows a cord circuitat the position ot a terminating operator in an ottico equipped forextending calls in accord ance with oral directions received from theoriginating toll operator, together with means for automaticallyassociating the operators head set with the cord circuit taken for use.

Figs. l to 8 inclusive, when arranged with Fig. i). at the right of Fig.l, Fig. 3 beneath Fig. Q, Fig. il at the right of Fig. Q, Fig. 5 beneathFig. il, 6 at the right of Fig. il. Fig. 7 at the right of Fig. 6, andFig. 8 beneath Fig. 7, show as much of a complete organization ofcircuits as is necessary to illustrate the manner in which a connectionmay be established from a calling subscribers line in an originatingoffice X to a subscribers line in a terminating office Z which isequipped for switching in accordance with call indicator linedesignations. Figs. l to 6 and 9 when arranged as above indicated butwith Fig. 9 substituted for Figs. 7 and 8 and placed at the right otFig. 6. shou as much of a complete organization ot circuits as isnecessary to illustrate the method of extending calls to a terminatingoliice -W equipped for straight-'forward switching through call circuittrunks.

The apparatus disclosed in Figs. l, 2, and 3 is located at oliice X,that shown in Figs. l, 5, and 6 at an intermediate otlice Y, thatshownin Figs. 7 and 8 at a terminating ottice Z, while that apparatus shownin Fig. 9 is located at a second terminating oilice lV. Like apparatusat the two oli'ices X and Y will be designated by the same referencecharacters without primes at the otlice X and with primes at the ofliceY.

Referring to the drawings there is shown a toll trunk line L comprisingtwo talking conductors extending from the originating oliice X to theintermediate oiiice Y. At the originating otlice X there are provided aplurality of toll cords one of which is shown at F, by means or" whichconnection may be Sil I irl established with the trunk line L. The trunkline L terminates at the ofiice Y in an oflice selector switch H, bymeans `of which the tollv line L may be connected with any one of theterminating oiiices such as Z or l or with a full mechanical exchange(not shown), and also terminates in multiple terminals appearing bef'orea plurality of linder switches, one of whichis shown at K.

At the terminating oliice Z the trunk lines extending from the bank ofselectors H one of which is shown in Fig. 7 terminate in plug terminalsby Vmeans of which connections may be extended to subscribers7 lines inthe terminating oiiice, one of which lines is designated as B.Connections are eX- tended at the ofiice Z in accordance withdesignations set up upon the call indicator shown at I in Fig. `S, whichindicator is common to a plurality `of terminating trunks and `isassociated `with any one of such trunks bymeans of a finder switch shownat M. l

At the ofiice W,- each of the trunk circuits, incoming from the bank ofselectors H, terminates in a calling plug by means of which connectionsmay be extended to subscribers lines, one of which has been designatedB. At this ofiice the operators set O may be associated with any one ofthe incoming trunk circuits by means of a finder switch N.

The selector switch H at the intermediate ofiice Y may, in addition tohaving access to terminating ofiices Zl and W, have access in thewell-known manner to trunk circuits eX- tending to full mechanicaloflices. As the apparatus usually employed in such mechanical offices iswell-known, it is not deemed necessary to illustrate such apparatus inthe drawings.

1While only onetoil cord circuitone toll trunk line, one oiiice selectorswitch H. one terminating trunk at `the otiice Z, one ter-- minatmgtrunk at the oiiice W, and onesubscribers telephone line' at each ot theoffices Z and W have been shown, it isto be understood that this is forthe purpose `ot convenience onlyand that as many ot such circuits andlines may be provided as are necessary to meet the requirements' of thetrafiic.

The supervisory signals for supervising calls overa plurality of tolltrunk lines may `be controlled over a single signaling path common tothe trunk lines and comprising a conductor P extending from theoriginating oiiice X to the intermediateoiiice Y, which path is shown ashaving a grounded return. The signaling path is arranged in a well-knownmanner for duplex operation, for which purpose there are provided at theends the artificial balancing lines AL and i'liiiieientiallybalancedrelays 25 and 25. Each end of the common signaling conductor Pis connected with a commutatoi' tor sending and receiving signals. Thesecommutators vare preferably of the wellknown start-stop type ofdistributors employed in connection with printing telegraph systems.Such commutators are dis` ollice Y, and similarly the commutator at ithe cnice Y comprises a sending distributor S and a 'receivingdistributor R for tra-nsniitting signals, to, and receiving signalsfrom, the oflice X-over the conductor P. These commutators at bothvoflices X and Y are of the same construction and a description ot onewill be sufiicient, and for convenience the construction of the sendingand receiving distributors S and R will be described. The sending.andreceiving disti-ibutors S and R each comprises a series ofstationary rings, some of which are continuous and others segmented. Acommon shaft `for the distributors has brush-arms 9 yand 10 mountedthereon andnormally held against rotation by the respective armatures oftwo separately controlled release magnets SRM and HRM. The outer end ofeach kbrush-'arm is insulated from the inner end so that each brush-armcontrols two separate groups of circuits. Between the common shaft andeach brush-arm there is rovided fiictional clutch mechanism ljnotshown.) by means of which the constantly rotating shaft causes therotation of each brush-arm when released. The face of the sendingcommutator S is stationary and is provided with a common sending ring14, a restoring segment fr, a start segment s, and individual sendingsegments 1 to 6 for controlling the signals transmitted over thesignaling conductor P, and with a common ring 15 and segments 16, 17,and 18 for controlling local circuits.' The face of the receivingdistributor R is also stationary and lis provided with a commonreceiving ring 19 and individual receiving segments 21 to 26 forselecting a circuit according to the code of signals received over thesignaling conductor P, segments 27 and 28, through which the signal iscompleted, segments 29 and 30 for controlling the circuit lof theassociated release magnet and a ring 31 ment 19 and the alternatecontact is connected with the segment 29. W'hen. the relay 25 isoperatively energized the re lease magnet BRM is energized to releasethe bruslrarm 10. :it the intermediate oiiice Y the common conductor Pis connected with the common sending segment 14, while the normalcontact ot the differential polarized relay 25 is connected with thecommon receiving segment 19, and the alternate contact of this relay isconnected with the segment 29. vWhen the relay 25 is opera tivelyenergized, the release magnet RRM is energized to release the brush-arml.

The codes ot signals transmitted over the conunon signaling conductor Pby the sending distributors S and S are determined by the polarity ofcurrent connected with the individual sending` segments et therespective sending distributors S and S. rlfhese polarities aredetermined by the position of the brushes ot automatic selector switchesG and G provided at the respective ottices X and Y. These auton'laticselector switches which are conunon to a plurality of toll trunk linesare alike in structure. The automatic selector switch G is provided witheight brushes a, b, c, d. e, 7', g, and 71, mounted upon a single shaftdriven by a motor magnet hldl, initially controlled by a start relay 200connected to the start conductor or start lead ST common to a group oftrunk lines. Brushes c to 7L, inclusive, are connected directly with therespective individual sending segments l. to 6 of the sendingdistributor S. Brush a is connected with one windingl of stop relay 201which controls the circuit of the motor magnet MM and the energizationof the release magnet SRM of the sendingdistributor S. Brush Z) isconnected with a contact of relay 202 for the purpose of assisting inthe control otthe switch, as will more fully appear hereinutter. Relay202 and a release relay 203, associated with the automatic selectorswitch G, are controlled by the sending distributor S tor reasons whichwill more tully hereinafter appear. A plurality of contacts, equal totwice the number ot toll trunk lines to which the automatic selectorswitch G is common, is associated with each brush on selector G. Thecontacts associated with the different brushes are mounted at differentlevels in position to be engaged by the respective brushes as they arerotated by the motor magnet MM, Two correspondingly positioned contactso t all levels are allotted to each trunk line; tor example, the irsttwo contacts may be allotted to trunk line No, l, the second two totrunk line No. 2, etc. The two contacts ot levels a and Z) allotted toeach trunk line, are connected with relays indi idual to and associatedwith the outgoing end of the trunk line. rl`he trunk line L has beenshown associated with the iirst two contacts of each level of switch G.As shown, relays individual to the outend of this trunk line areconnected by means otl individual signal control leads e, 205 andrestoring leads 206 and 207 with the allotted contacts accessible tobrushes (L and signal control leads 204; and 205 being connected to therespective first and second contacts of the level to which 1orush a. hasaccess and restoring conductors 206 and '20T to the respective first andsecond contacts olf the level to which brush 7) has access. Each trunkline is provided with similar signal control and restoring` leads at theottico similarly connected with the selector switch G. The automaticselector switches, shown in the drawing, are provided with sufficientcontacts to accommodate thirty trunk lines. To the contact of the levelsto which brushes c to 71, have access allotted to the respective trunklines, are connected current sources oi the polarities in combinationsas indicated in the tollowing table, there being a differentcoinbination for each trunk line and also tor the two contacts allottedthereto;

The automatic selector switch G allotted at the intermediate oliice Y,is like the switch Gr in structure and is associated with the sending`distributor S in the same manner as switch G is associated with thesending distributor S, with the similar start relay 200 and motor magnetMM and with switch G is associated with the toll trunk lineL, shown inthe drawings, by means of' the individual signal. control leads 204 and-205and restoring lead 206 and a common start lead ST, individualconductors 204 andl 205 being connected with the allotted first andsecond contacts ofl level a, individual restoring conductor or lead 206with both allotted contacts of the level o and the common startconductor ST with the start relay 200 .ofV the switch G. The selectorswitclji`- G is associated With each `of the` other trunk lines throughsimilar signal control and restoring leads, The polarities connectedwith the individual sending segments 1 to 6 of the sending distributor Sare determined by the position of the brushes c to it of the switch G',andthe different combinations of polarities connected with4 the allottedfirst and second contacts of thelevelsto which brushes c to 7L haveaccess for the various trunk lines are identical with those connected tothe automatic selector switch G, as shown in the preceding table.

lIn order t-hat the signals transmitted from the originating office X bythe sending distributor S and received at the office Y may be utilized,there are provided at the office Y six locking relays 41 to46 inclusivehaving energizing windings connected with the respective individualreceiving segments 21 to 26 of the receiving` distributor R. When anegative impulse is transmittedfrom a particular individual sendingsegment, the relay connected with the corresponding individual receivingsegment will be energized andxlocked up. Relays 41" to 44 control aplurality of receiving and selecting relays 50 to 64 inclusive whichcooperate with relay 45 to select a signal control circuit individual toa'trunk line, while relay 46 controls the polarity of current connectedwith the selectedsignal control circuit. The individual signal controlcircuits are connected with contacts of relays to 64" inclusive.Similar' equipment is provided at originating oice X for utilizing thesignalstransmittted from the intermediate office Yk over the commonsignal `conductor P.

The selector switch H, shown at the intermediate office Y, is of thestep-by-step type similar to that disclosed in Goodrum Patent 1,231.013,issued lune 26, 1917. The finder switch, designated K, is of thewell-known rotary step-by-step type and is employed to connect animpulse repeating? device indicated by the dotted rectangle 600 with theincoming end ofk a toll trunk line L. This repeater may be of' the typedisclosed in Patent to rie lo.y 1,202,925 issued October 31, 1916.

The call indicator shown at I in Fig. 8

scribers station A, over toll trunk line L comprises a switches which,through transfer relays, are connected in succession to a local steppingcircuit and are under the control of impulses repeated over the trunkline extending from the terminating office Z to the intermediate officeY by the repeater 600 at the office Y. Each of the step-by-step switchesof the register is provided with a bank having ten terminals which areconnected .with indieating lamps. The indicator I is associated with thetrunks terminating in the office Z by means yof a step-by-step switchMof the` well-known rotary type. t

The toll operators position in office Xj is provided vwith a highfrequency impulse sending device diagrammatically shown by the dottedrectangle 10,0 and of the type shown in the patent to C. R. Englund No,1,245,446 issued November 6, 1917, which is under the control of theoperators impulse sending dial 101, This impulse sending device 100 maybe associatedl with cord circuit F atl the operators position by `meansof a key.102. Having in mind this brief description of the apparatus ofthe system shown in the drawings, itis. thought that the invention willbe more thoroughly understood from a description of the operation of thesystem shown, and therefore a description of the method of extending acall from the'sub- 7 through the intermediate office Y, and toV thesubscribers. station B in terminating offlee Z will first be explained.

The subscriber, whose substation is designated A., desiring to establishconnection with theL subscriber, whose station is designated B, whichline terminates in the terminating office Z, will, in any well-knownmanner, as through an originating operators position (not-shown) and a.switching trunk, obtain connection with ators position at ofiice X,shown in Fig. 1. The operator in response to the call inserts theanswering plug 103 of the idle cord circuit F in the jack 104 of theswitching trunk, thereby causing the energization of sleeve relay 105.Relay 105 upon energizing closes the tip strand of' the answering end ofthe cord circuit, thereby enabling the toll operator to converse withthe calling` subscriber A, or with the operator at the originatingoffice, as soon as the toll operator throws her listening key 106 toconnect her head set with the answering end of the cord circuit F. Uponascertaining that the calling subscriber A desires connection with thesubscriber in an office which is accessible over the toll trunk L, thetoll operator inserts the calling plug 107 of the cord circuit F inthejack 108 of an idle toll trunk L, which is selected by testing in thewell;- known manner. v

plurality ef rotary stepfbrstep los the toll operleo e A. circuit is nowestablished extending from grounded battery through the winding ormarginal sleeve relay 109, the right-hand Winding ot' relay 110, oversleeve conductor 111, through the sleeve contact ot plug 10T, the sleevecontact otjack 108, the Winding of relay 208, and thence to groundthrough the Winding of marginal relay 209. Relays 110 and 20S operatebut relays 109 and 209 do not operate at this time, owing to theirmarginal nature. Relay 208, upon energizing, closes a circuit 'for relay210, which circuit may be traced from grounded battery through the innerleft-hand armature and back contact of relay 211, the Winding of relay210, and thence to ground through the front contact and armature ofrelay 208. Relay 2107 upon energizing, closes a locling circuit 'foritself extending from grounded battery through its inner lett-handarmature and front contact, the Winding ot relay 210, and thence toground at the armature and :tront contact ot' relay 208. Relay 210 alsocloses an energizing circuit tor relay 211 Which may be traced fromgrounded battery through the outer left-hand front contact ot relay 210,and thence to ground through the left-hand Winding of relay 211. Relay211, upon energizing, closes a locking circuit for itself extendingthrough its inner lett-hand armature and t'ront contact, and opens atthe back contact ot this armature the initial energizing circuit ofrelay 210.

Upon the energization of relay 211, ground is connected to the startconductor ST over the intermediate left-hand armature and front contactof relay 211, the.

right-hand armature and back contact of relay 212, and the right-handarmature and back contact oit relay 213, and ground is connected tosignal control conductor 205 over the outer left-hand armature and frontcontact of relay 211, the outer right-hand armature and front contact otrelay 210, the

` left-hand armature and back contact of relay 212, and the outerleft-hand armature and back contact of relay 213.

"Relay 200 nonv energizes over conductor ST and closes a circuit tor themotor magnet MM extending from grounded battery through the armature andcontact of magnet MM, the left-hand armature and back contact of stoprelay 201, and the front contact and armature ot relay 200. Motor magnetMM, upon energizing in this circuit, advances the brushes ot thedistributor switch G over their respective levels of con tacts until thebrush a linds a grounded conductor 205 corresponding to a toll trunkwhich has been taken for use by the toll operator. Assuming that theconductor 205, corresponding to the toll trunk L, is the first groundedconductor to be encountered bv the brush a, a circuit is established forthe stop relay 201 extending 'trom grounded battery through theleft-hand Winding of this stop relay, through the brush a, overconductor 205, and thence to ground as previously traced at the outerleft-hand armature of relay 211. The stop relay 201 upon energizing,opens the circuit of the motor magnet MM and thereby arrests themovement of switch G. Relay 201 also closes a lockingcircuit for itseltlextending from grounded battery at the armature and back contact otlrelease relay 203, through the inner right-hand armature and frontcontact of relay 201, and the right-hand winding thereof to ground.Relay 201 also closes a circuit 'for release magnet SRM ot the send ingdistributor S, which circuit extends trom grounded battery through thering 15, the inner brushes of the brush-arm 9, segment 16, the frontContact and outer righthand armature of relay 201, and thence to groundthrough the winding of the release magnet SRM. The attraction ot thearmature ot the release magnet SRM, upon the energization thereof,releases the brush-arm 9, which is thereupon rotated through a completecycle, at the end ot' which the brush-arm is stopped in its normalposition. The brush-arm 9, in being rotated. first engages start segments, thereby connecting positive current With the common signalingconductor P.

Brush-arm 9 then moves out of engagement With segment 16, therebyopening the energizing circuit of and causing the deenergization ofrelease magnet SRM, which restores its armature to normal positionpreparatory to stopping the brush-arm when it reaches its normalposition. From an inspection of the table ot polarities it will beobserved that when the switch G stopped with its brushes in engagementWith the irst of the two contacts in the several levels, allotted totrunk line L, that positive current is connected with such lirstcontacts on levels c, d, f, g, and h, While negative current isconnected with such first contact ot level c.. Vhen the inner brushes onbrush-arm 9 engage segment 17, a circuit is closed extendingfrom batterythrough ring 15, the inner brushes on arm 9, segment 17, and thence toground through the Winding ot relay 202. This relay, upon energizing`closes a circuit extending from grounded battery through the armatureand back contact o1" relay 203, the armature and Vtrout contact ot relay202, over the brush Z) ot switch G, conductor 20G, winding of relay 213,right-hand armature and bacl contact of relay 212, and thence to groundthrough the left-hand intermediate armature and front contact of relay211. Relay 213 energizes in this circuit and at its inner lett handarmature establishes a locking circuit for itseliz independent ot thecircuit extendieri kes

43 and thereby the circuit through the windings of relays 5l and 5". Thecircuits or thesignal receiver are now in normal position' in readiness'for the receipt and translation of other code signals. It is to benoted that during the rotation o1 the receiving distributor, relays 41',42, 44, 45', and 46 were not Aenergized inasmuch as relay 256 washolding its armature against its alternate contact at. the time thebrushes on switch arm 10 were passing over segments 21', 22', 24', 25,and 26 con nected respectively to these relays.l

Relay 400 at the intermediate oi'lice Y, upon .energizing over thecircuit traced through conductor 500, closes a locking circuit foritselic extending from lgrounded battery through its right-hand winding,and

to ground through its inner right-hand ar-v mature and front contact.The energization of relay 401 is without ellfect at this time and thisrelay deenergizes as soon as the receiving distributor R reaches normalposition and opens the circuit over conductor 500. Relay 400, uponenergizing, valso bridges the polarized relay 402 across the incomingend of the t-oll trunk line lL, through its outery armature and frontcontact, and at its inner armature and front contact closes a circuitextending through the right-hand armature and back contact oi' relay401, and through the winding of slow-releasing relay 403. Theenergization of relay 403 is without function at this time. A circuit is`also established from battery at the inner arman ture and back contactoit relay 601, the winding of relay 602, conductor 606, conductor 404',and thence to ground at the inner armature and 'front contact of relay400.

Relay 602 energizes in this circuit, if relay 601 is at the timedeenergized, closing a circuit extending from grounded battery throughthe Winding Vof starting relay 604, the armature and front Contact or"relay 602, and thence to ground through the left-hand armature and backcontact of relay 605 and resistance 606.' Selectable potential is alsoconnected over the circuit above traced to the lowermost bank contact607 of finder switch K. y

Upon the energizatiou of relay 604, a circuit is closed through themotor magnets 608 of all linder switches which are at the time idle. Acircuit for the motor magnet of finder switch K, shown in Fig. 6, maybel traced from grounded battery through the motor magnet 608, thearmature and back contact of this magnet, `the armature and back contactof stop relay 609, and thence to ground at the armature and frontcontact of relav 604. The inder switches which are started up willcontinue to move their brushes over their respective banks of contacts,which contacts are individual to ously traced to the contact 607,vthence overy brush 610, and to ground through the winding of stop relay609. Relay 609 energizes in this circuit opening at itsouter armatureand back contact the circuit extending through motor magnet 606, and atits inner armature and front contact closes a circuit extending fromgrounded batterythrough the winding of relay 611, and thence to groundat the inner armature and front con'- tact oit relay 609. t

`Relayv611, upon energizing, connects the input side ofrepeater 6 00over its armatures and front contacts, brushes 612 and 613 of linderswitch K, contacts 614 and 615 with which they are in engagement,

thence over conductors 616 and 61'?, through Y the intermediate andouter leftehand armatures and bacl-r contacts of relay 601 to the y tipand ring conductors of the toll trunlr A circuit is also closed at thistime from grounded battery through retardation coil l 616, the upperarmature and front contact ol relay 611, brush 612, contact 614,conductor 616, the intermediate armature and back cont-act of relay 601,the/inner armature and back contact of relay 405, the upper right-handwinding of `repeating .coil 414 the windings of polarized relay 402, theouter armature and front contactof relay 400, the lower right-handwinding of re-y peating coil 414, the outer left-hand'armature and backcontact otrelay 405, vthe outer left-hand armature and bacl; contact or'relay' 601, conductor 617, bank contact 615 of linder switch K, brush613, the lower armature and front contact of relay 611, retardationcoil619,v and thence to ground through the ,winding of-relay 609. Acircuit is also established at this time for relay 605, which circuitmay bev traced from grounded battery through the inner armature and backcontactol relay 601, wind-y ing of relay 605, bank contact 620, brush621, and thence to ground through the inner armature and front contactof relay 609; Relay 605, upon energizing, opens the circuit of relay604, which, if there are no other incoming calls on other trunks oftheing through brush Z1 of switch Gr, at its outer lett-hand armature opensthe circuit extending over conductor 205, and at its right-hand armatureopens the starting conductor ST.

As the brush arm 9 successively moves its brushes over the individualsending segments 1 to G, current sources oi the polarity connected withthese segments are successively connected with the conductor l). Whenthe brush-arm 9 moves its brushes out of engagement with segment 17, theenergizing circuit of relay 202 is opened, and upon the engagement oi'the inner brushes on brush-arm 9 with segment 18, a circuit isestablished for release relay 203, which extends from grounded batterythrough ring` 15, the inner brushes on arm 9, segment 18, and thence toground through the winding of relay 203. Relay 203, upon itsenergization, opens the locking circuit of relay 201, whereupon thisrelay releases As the brushes on arm 9 move out ot engagement withsegment 1S, release relay 203 is deenergized. When the brushes onbrusharm 9 engage the restoring segment r, current of negativepolarityis connected with the common signaling conductor P, and theautomatic selector switch G now in condition to be seized by anothertrunk since the trunk line L is now disconnected therefrom and thesending distributor S is in normal condition.

rIhe connection of positive current .trom segment s with conductor Pdoes not affect differential polarized relay in oilice but causes theoperation of the differential polarized relay 25 at the intermediateottice Y over a circuit extending from positive battery through segments, the outer set ot brushes on arm 9, the common sending ring 14, andthe unction point between .the windish ings of differential polarizedrelay 25, then by one path through the lower winding of relay 25 andartificial line AL to ground, and by another path through the upperwinding of relay 25 conductor P, both windings of the dil'erentialpolarized relay 25 and the articial line to ground` The operation ofrelay 25 establishes al circuit extending from grounded battery throughthe alternate contact of relay 25, segment 29, the outer set of brusheson arm 10 of the receiving distributor switch R, segment 30 and thenceto ground through the winding of release magnet RRM. The attraction ofthe armature of the release magnet. upon the energization thereofreleases the brush-arm 10, which is thereupon rotated through a.complete cycle at the end ot which the brush is stopped in its normalposition` As the brush-arm 10 moves its brushes out of engagement withthe segments 29 and 30', the circuit extending through the releasemagnets RRM is opened, and the magnet deenergized, permitting therestoration .of its armature to normal position preparatory to stoppingthe brush-arm when it reaches its normal position. vWhen the brush-arm10 moves its inner set of brushesinto engagement with the segment 32, acircuit is established extending trom grounded battery through the ring31', the inner set of brushes on the brush-arm 10, segment 32, andthence to ground through the winding` of relay 82. `lelay 82 thereuponenergizes, connecting atv its armature and front contact a holdingground to the conductor S3', which is common to the locking circuits ofrelays el to 46 inclusive. rfhe armature of the polarized relay 25remains in its alternate position as long as positive current isconnected with the other end of conductor P and moves to its normalposition whenever negative current is connected with the other end otconductor P.

The brush-arms 10 and 9 are rotated synchronously, and whilebrush-arm 9positions its brushes in engagement with segment 3 of the sendingdistributor S, to which negative current is connected, the armature oirelay 25 moves to its normal position and brush-arm 10 positions itsbrushes in engagement with the receiving segment 23. Relay L13 isthereupon energized over a circuit extending from grounded batteryvthrough the normal Contact of relay 25, segment 19 of the distributorR', the outer set of brushes on brush-arm 10, segment d3', and thence toground through the lower winding of relay 43. This relay, uponenergizing, locks itself to the grounded conductor 83', through itsupper winding and its upperarmature contacts. At its lower armature andfront contact, relay 43 closes a circuit extending from grounded batterythrough the windings of relays 5., and 51', which thereupon energize.Then the brush-arm 10 positions its brushes upon segments 2i" and 28',just prior to reaching its normal position, a circuit is establishedextending from grounded negative battery through the lower armature andback contact ot relay 46', through segment 27, the outer set of brusheson brush-arm 10, segment 28', the lower armature and back contact ofrelay 4-5, the lower armature and baclr contact ot' relay 50, the lowerarmature and front contact oit' relay 51, the upper armature and backContact of relay 53, the upper armature and back contact of relay 58,thence over conductor 500 which is individual to the toll trunk L, andto ground through the left-hand winding of relay 400 and the right-handwinding of relay l101. As soon as brush-arm 10 moves its brushes beyondthe segments 27 and 28, the circuit existing through the winding ofrelay 82 is opened, and this relay dcenergizes opening the lockingcircuit ot relay oiice selector switch H, this circuit extending'fromgrounded battery through the of relay 62.2.'Relay 622,-'I uponenergizing,

closes a circuit for slow-release relay 628, which may-betraced fromgrounded .battery lthrough the winding of this relay, `and thence toground through the armature Vand front contact of relay 622. Thecircuits of the repeater 600 and of thev office selector switch H are now in condition .to receive directive impulses for causing ltheselection of the desired terminating .oice

When relay 611 energized and established a circuit through the windingofpolarized relay A402, said relay energized in such a manner as to moveits armature into engagement with its let-handncontact, thereby closinga circuit for slow-releasing relay 406, slow operating relay 407, andrelay 408, and causing the energization. of these relays. A circuit forrelay 406 may be traced from grounded battery through the winding ofv.this relay, the armature and lefthand contact of relay ,402,- andthence to ground at the inner armature and front contactof relay 400.,The circuit of relay 407 may be `traced ,from vgrounded battery throughthe winding of this relay, the norinally closed make-before-breakarmature contacts ofthis relay, the right-hand armature and back contactof relay 409, the outer right-hand armature and back contact of relay410, the armature and left-.hand contact of relay 402, and thence toground at the armature andcontact of relay 400. Re. lay 407, uponenergizing, closes a locking circuit for itselt'through its right-handarmature and make contact, the outer .left-1 hand armature and backcontact of relay 411, and ,thence to ground over the circuit previouslytraced, through thearmature and left-hand contact of relay 402. Relay407 thus remains under the control of relay 402 until relay 411 isoperated. The circuit of relay 408inay be traced fromY groundedbatterythrough the windingV of relay ,412, the v Vouter left-hand armatureandback contactofrelay 409, the winding of relay 408, the

break contacts ofits inner right-liand armature, the lefteliand armatureand/back contacts of relay 407the right-hand armature andback contact ofrelay 409, and thence tovground over the circuit previously traced,

through the armature contactsjof relay 402. Since relay 407 is slightlyslowrto energize, the circuit of relay 408 is estab-k lishedy beforerelay` 40'( energizes to'open its left-hand armature contacts. Relay408, upon energizing in the circuit previously traced, closes a lockingcircuit for itself, extending` through the winding of relay 412left-'hand armature and back contact of relay 409, its own winding andthe make contacts of its inner right-hand armature lto ground.

The energization of relay 406prepares a circuit for the slow-releasingrelay 413, which circuit extends to 4the right-hand armature Contact ofpolarized relay 402, and isclosed as soon as the directionk of currentflow .is reversed throughthe winding of relay 402. Relay 408, uponenergizing, closes a circuit for relay 420 extendinofrom groundedvbattery through the winding of relayv420, the left-hand armature andback contact of relay 419, and thence to ground at the inner left-`handarmature and front contact of relay 408. Relay 420 energizes in thiscircuit and closes a locking circuit for itself, extending through itsarmature and front contact, the winding of ielay419, the innerright-.hand armature and back contact ofrelay 410 to ground at the innerarmature andy front contact of relay 400.y

Relay 419, however, does not energize in this circuit since its windingis shunted by ground at the armature and contact of relay 408. Relay412, which energized in series with relay 408 upon energizing, closes acir-k cuit for the start relay 200` of the selector switch G', which,upon energizing, closes a circuit for lthe motor magnet MM of thisswitch, which circuit extends from groundl edbattery through armatureand back contact and winding of the motor magnet,

through the right-hand armature and back contact of stop relay 201', andthence to ground through the armature and front con tact of relay 200.The switch G is thereupon started to move its brushes over theirrespective'levels of contacts, until the brush a engages the contactconnected by conductor 205 to ground at the outerlett-hand armature andfront contact of relay 408, this conductor being individual'to theincoming end of the trunk line L, when va circuit .is establishedthrough the right-hand winding of stop relay 201. This stop relay`energizing in this circuit, opens the circuit of the motor magnet MBL',and closes a locking circuit for itself,` extending from groundedbattery through the armature and back contact of relay 203, through theVinner left-hand armature and front contact and left-hand winding ofrelay 201r to ground. At its outer left-hand armature and front contact,stop relay 201 closes a circuit extending from grounded battery throughthe ring 15', the inner-brushes on brush-arm 9', segment 16', the outerleftllO ' grounded battery through the and in the manner previouslydescribed inv connection with the sender distributor S, transmits a codeot signals comprising two positive, a negative, and three positive iinpulses, which are received by the receiving distributor R at theoriginating oiiice X to lock up relays 43, 51 and 52 in the saine'manner as previously described in connection with the receivingdistributor R. The send ing distributor Sl, after leaving its normalposition, closes a circuit :tor rel-,ay 202, extending from groundedbattei'y through the ring 15', the inner set of brushes of thebriish-arm 9, segment 17 and winding of ielay 202 to ground. Relay 202',upon energizing, closes a circuit extending from armature and backcontact ot relay 203, the armature and front contact ot relay 202', overthe brush 7) having access to the second level of selector G', conductor206', and thence to ground through the winding ot relay 409. Relay 409,upon energizing, opens the circuit ot relay 408, causing thedeenergization of this relay. The shunt around the winding ot relay 419is now opened and relay 419 energizes in the locking circuit ot relay420 for a purpose to be described hereinafter.

The receiving distributor R, it will be understood, is started at thetime sending distributor S is started and rotates in synclironisintherewith, and ust before reaching l its normal position closes acircuit extend ing from grounded negative battery through the lowerarmature and back contact of relay 46, the segment 27, the outer set etbrushes of the brush-arm 10, segment 28, the lower armature and backcontact ot relay 45. the lower armature and back contact of relay 50,the lower armature and front contact ot relay 1, which together withrelay 52, was energized by the operation ot relay the upper armature andback contact ot relay 53, the upper armature and back contact of relay58, thence over conductor 300 to ground through the right-hand windingor" relay 214. Relay 216 does not operate Vat this time over conductor300, since its circuit, which is normally in parallel with the winding`oi" relay 214, is opened at this time through the armature and backcontact ot slow-releasing relay 215 this relay having been previouslyenergized bythe operation ot' relay 208. Relay 214, upon energizing inthis circuit, closes a locking circuit tor itself extending fromgrounded battery through its lett-hand armature and front contact. itslett-hand winding, and thence to ground at the armature and frontcontact ot hand armature and back contact et relay 216,

through the right-hand armature and front contact oit relay 214, throughresistance 217,

and thence over the sleeve conductor ot the trunk circuit L, through thesleeve et ack 108, sleeve ot plug 107, conductor 111, winding ot relay110, and winding oi marginal relay 109 to grounded battery. Theconnection oit resistance 217 in parallel with' the windings of relays208 and 209 changes the resistance ot the sleeve circuit sufficiently topermit the operation of marginal relay 109 of the toll cord circuit F,which relay, upon energizing, closes the circuit of the lamp 112` whichat this time serves to give the toll operator a. dialing signal toapprise her ot the tact that the finder switch K has associated animpulse repeating device 600 with the incoming end ot the toll trunkline L, and that she may now proceed to dial the digits required to setthe switch H on the tern'iinals ot the trunk line extending to thedesired terminating oflice Z, and the digits required to set up thenumber ot the desired line in this ottice upon the lamp indicator I.

It will be assumed that the calling subscriber desires connection withthe line ot the called subscriber l, whose directory number is 1920 -J.rllie toll operator will thereupon throw her dialing key 102 to connectthe impulse sending` device to the strands ot the cord circuit F. Uponthrowing the key 102 acircuit is closed 'from ground through contacts113 of the key. and through the lett-hand winding of relay for holdingthis relay positively energized during the transmission et the dialingimpulses to in sure that the tip strand of the calling lend oi the cordcircuit is maintained closed. At its lowerinost alternate contact 114,the key 102 closes a circuit extending trom grounded battery directly tothe sleeve conductor 111. in parallel with the windings of relays 109and 110, which so increases the flow ci cur rent over the sleeveconductor that marginal relay 209 now becomes energized. Relay 109releases while the dialing key 102is operated, and extinguishes lamp112. Relay 209, upon energizing, closes a circuit for relay 212, er;-tending from grounded battery through the winding ot relay 212, andthence to ground through the armature and front contact oit relay 209.Relay 212, upon energizing, opens the locking circuit of relay 213,permitting relay 213 to deenergize, thereby connecting start conductorST and the impulse control conductor 205 to the back contacts of the CIIlll)

designation of the desiredline for setting the ofiice selector switch H.When the dial is released after itsinitial setting and returns Y tonormal, the circuit of lrelay 115 is intermittently opened, therebycausing the lassociation of the impulse sending 'device 100 with theimpulse conductors 11,6 and '11.7, a number of times corresponding `tothe-setting of the dial, and sinceatthe ytime the operator listened -inonfthe connection'f'by throwing 'the listening key 106, the Vrelay i1118was energized-over a circuit extending from battery through :the windingof this relay and the alternate contacts 119 of key 106, the impulseconductors 116 and 117, are now connected over contacts 120 and'121 ofthe dialing'lrey 102, through the tipand ring strands of the cordcircuit F, over; the tip and ring contacts of the plug 107 and -the'jack108, and thence to thetip and ring conductors of the toll trunk line "LUpon the movement of the dial 101 oli' normal, the off normal contacts122 vof the dial closea circuit extending from vgrounded ibatterythrough these contacts, the left-hand armature and front contactot relay1115,andto groundthrough the winding of slow-releasing relay 123, which,due toits slow-releasing character, maintains a circuit forthelamp124'solong as the diallOlis oifnormal. I The sending device vis designed'for transmitting high frequencyalternating current'impulses outover'the toll trunk, these impulses having-a lfrequency of preferably800 cycles. 'These impulses are repeated through the several repeatingcoils of the trunk circuit `L andflow throughthe input circuit oftherrepeating devicef600 atgthe intermediate oiice Y. These impulses,throughy the well-known construction ofthe repeating Vdevice 600, `causethe intermittent operation of the repeating relay V629. Y Uponeach'energization, relay 629 closes a circuit extending 'from groundedbattery through the winding of relay 625,' over bank contact 630 of the{inder-switchK, wiper631, and thence to grou-ndA at the armature andfront contact vof relay`629. Upon each energiza? tion, relay 625 opensthe bridge ofthe'incoming end of the trunk circuit L, extending throughvthe resistance 626, thereby causing the deenergization of line relay',622 of the selector switch H. vUpon each deenergization a circuit isclosed from grounded battery through the winding of vertical steppingmagnet 632, winding oftheislow-releasing relay 633, theleftlhandarmature and front contact of slow-releasing relay 628 which,

because otits slow-releasing character, does not deenergize upon shortopenings of its circuit at thearmature and front contact of relay l6,22,thence through the right-hand armature and back contact of relay 623 toground at the back contact of line relay A622. In response to eachldeenergization of line relay 622, vertical magnet 632V steps the switchshaft of the selector switch H up one step. Slowreleasing relay 633,which energizes in series with stepping magnet 632,

upon its initial energization close a circuit extending from grounded'battery through its armature and front contact, and thence to groundthrough the winding of private relay 634. This circuit is maintaineduntil thestepping impulses cease, and since Von the lirststep off normalof the switch the off normal contacts ON were closed, the relay 634 isnow maintained energized over a locking circuit extending from groundedbattery through the right-hand armature and front contact of relay 628,the lefthandv armature and back contact or" the rotary magnet 635,contacts 636 of the oi normal switch ON, the left-hand armature andfront contact and winding of relay 634L to ground. The relay 634- istherefore maintained energized after the vertical movement of theselector switch yshaft has Vbeen com-y pletedand the relay 633 hasreleased its armature. l

yUpon the deenergization of slow-releasing relay 633 follow-ing thetermination of the lirst group of impulses, a circuit for therotary'magnet 635 is closed extending from grounded battery through theright-hand armature and front contact of relay 628, the left-handarmature and back contact of rotary magnet 635, contact 636 of oilnormal switch ON, left-hand armature and front contact of relay y6311,armature vand back contact `of relay 633, right-hand armature, backcontact and winding of rotary magnet 635 to ground. Rotary magnet vv635energizesin thisficircuit -and interrupts itsown circuit at its armaturecontacts, thereby stepping the switch shaft one step intherotaryidirection.k Rotary magnet 635 also opens the-holding circuit ofthe private relay 6341 at itsleftehand'armature contacts, and privaterelay 634 deenergizes unless the test wiper 637 of the selector switchisat that timein engagement with the test terminal of a busy trunkextending to the desired oice, in which event this test terminal willbeconnected to grounded battery. Thus, so long as the test wiper 637engages the ter` ininals ofibusy trunk lines, `private vrelay 631- willbe maintained energized and rotary magnet 635 will continue to step thewipers of the switch over the selected row of trunk terminals, until theterminals of an idle trunk line are found when relay 634edei energizes,permanentlyI opening the stepping circuit of theV rotary magnet A635.

' When the testvwiper637 stops on a contact associated with an'idle-trunk, which trunk

